Well, This was neat and enjoyable. The idea of Machines becoming custodians of their human creators was a bit cliche, but I found it plausible. Even if they do decide to maintain their humans in a primitive society, rather than equal partners in the spacefaring and engineering projects.
The Problem at the end which spells the end of the machine culture, but not the humans, given that they are less susceptible to the hard radiation, just doesn't hold water. Just off the top of my head, several hundred miles of planet should block most radiation; or build a ship to put some machines on and get out of the way of the radiation for a while. The idea that they just accept extinction without considering alternatives doesn't make sense.
Still, it was fun, and I enjoyed it.